Geochronology and isotopic geochemistry characteristics of the Maoling large gold deposit, Liaoning Province, China

The Maoling large gold deposit, located in northern North China Craton, is an As-bearing disseminated gold deposit. The ore bodies are hosted in the metamorphic rocks of the Proterozoic Liaohe Group. The gold orebodies appear as veins, bedded, and lenticular, and controlled by NE-and NW-striking ductile shear belts and secondary faults. We present Rb-Sr ages from ten metallic sulfide samples which reveal the mineralization timing of the Maoling gold deposit as 2287±95Ma (MSWD=1.9), initial Sr isotopic value I_Sr=0.7117. The high precision LA-ICP-MS zircon U-Pb dating method has been applied to measure the ages of the Wolongquan and Maoling granitic intrusions in the Maoling deposit, corresponding the dated ages of 183.0±1.8Ma, 128.8±1.6Ma, respectively. The Late Mesozoic magmatic activities were not related to the formation of the Maoling deposit. The calculated δ¹⁸O water values of ore-forming fluids show a range of 6.3‰ to 9.7‰. The δD values range of -97.2‰ to -82.6‰. H-O isotopic data indicate the ore-forming fluids were mainly derived from magmatic fluid with minor metoric water. The δ³⁴S values recorded in the sulfide minerals from the Maoling deposit show a range of +4.3‰ to +10.5‰, averaging +7.9‰, similar to sulfur isotopic composition of the Gaixian Formaiton of the Liaohe Group. This evidence shows sulfur derived from strata of the Gaixian Formation. The Maoling gold deposit was formed in Paleoproterozoic extensional setting. The gold mineralization could be related to syntectonic magmatic hydrothermal activities in the early formation process of the Liaohe Group, and was not destroyed by later geological activitions as protection of contemporaneous strong silicfication belt.